05.03 · Concept
Trials, Coupons, Proration & Upgrades
Change a customer's plan mid-cycle and charge the right amount, and put a discount where the amount is computed rather than where it is displayed.
No video curated for this lesson yet
This lesson is written, ordered and part of the path - the video slot is the only thing still open. We are working through Payments lesson by lesson; 26 of 35 have their video so far.
The written notes below cover this idea in full - you lose nothing by reading instead of watching.
Mid-cycle subscription changes are timeline calculations: consumed entitlement, remaining entitlement, old-plan credit, new-plan charge, discount, tax and payment state. Coupons and trials must live in the billing calculation itself, so invoices, renewals, refunds, reporting and support all agree on the amount owed.
What this lesson answers
- how to prorate a subscription upgrade mid cycle
- where should coupon discounts be applied in billing
- how should trials affect subscription invoices
Notes
Trials, coupons, proration, and upgrades are all ways of changing what a subscription customer owes over time. The key idea is that the bill is not just “plan price times month.” It is a timeline of entitlements, billing periods, price changes, credits, discounts, taxes, and payments. When a customer changes plan mid-cycle, you need to decide what service they already consumed, what service remains, and how much value should be credited or charged for the difference.
A practical mental model is to split the billing period into used and unused time.
References
Common questions
- How should a subscription upgrade be charged mid-cycle?
- Treat the current billing period as partly used and partly unused. Credit the customer for the unused value of the old plan, then charge for the remaining value of the new plan. The invoice should show those lines separately, so the final amount is explainable and auditable.
- Why should coupons be applied in the billing calculation?
- A coupon changes what the customer owes, so it belongs in the same system that computes invoices, renewals, refunds, tax and revenue records. If it is only applied in the UI, the displayed price can diverge from what is charged or reported elsewhere.
- What product rules matter for trials and plan changes?
- You need explicit rules for whether trials convert automatically, when billing starts, how downgrades create credits, and which plans a coupon affects. Without those decisions, the code will embed accidental policy and customers may see inconsistent charges.